Senior Full Stack Engineer in London

About Synextra

Synextra is a Microsoft-specialist Managed Service Provider headquartered in Warrington, operating as a premium partner to regulated mid-market organisations including law firms, financial services firms, and mortgage lenders. We are deliberately small - around 35 people - because we believe the best outcomes come from technical depth, not headcount. Our development team is growing, building and deploying modern web applications and intelligent solutions for clients across the UK. This is a chance to shape our technical approach from the inside - the architecture, the standards, and the products.

The Role

You will drive technical architecture across Synextra's client projects - designing scalable full-stack systems, leading technical decisions across the Python and TypeScript stack, and building solutions that run securely and cost-effectively within our Azure estate. This is a hands-on senior development role where your architectural choices directly shape what we ship to clients. Day to day, you will work across the full delivery lifecycle: designing robust backend services and APIs, building performant React frontends, and collaborating with customers, product owners, and infrastructure specialists to deliver business-critical applications. You will own end-to-end technical delivery on our most ambitious projects - with increasing opportunities to incorporate AI/LLM capabilities as our AI Services Division grows. This role suits someone who thrives on complex distributed systems problems, has a genuine interest in the rapidly evolving AI/LLM landscape, and wants genuine autonomy over how things get built. You will also play a mentorship role - raising the engineering bar across the team as we scale.

Responsibilities

• Design scalable, secure, and fault-tolerant full-stack architectures, ensuring high availability and resilience across Azure-hosted environments.
• Architect robust backend services in Python using modern frameworks (FastAPI, Pydantic), implementing clean API design, efficient data pipelines, and integration patterns within our Azure ecosystem.
• Establish and enforce best practices for the TypeScript/React frontend, ensuring a highly performant, accessible, and intuitive user experience, including real-time interfaces and interactive data visualisations.
• Lead the configuration and optimisation of Azure cloud environments, establishing robust CI/CD pipelines with GitHub Actions or Azure DevOps, and ensuring cost-optimised use of Azure services and container orchestration resources.
• Set the standard for code quality through comprehensive code reviews, technical design documents, and architectural decision records; mentor junior and mid-level engineers to grow their capabilities.
• Champion engineering best practices including security-first development, comprehensive testing, and compliance with data protection regulations; contribute to emerging AI/LLM features as our capabilities expand.
• Identify patterns in recurring issues and engineer permanent solutions.
• Contribute to technical pre-sales and client engagements by providing architectural guidance, solution design, and effort estimation.

Job requirements

Requirements

Essential Technical Skills

• 6+ years of professional software engineering experience with a track record of architecting and delivering complex applications from concept to production.
• Expert-level proficiency in Python for backend services and data pipelines, including frameworks such as FastAPI, Pydantic, and async patterns.
• Strong proficiency in TypeScript and React for building production-grade frontends, with solid understanding of state management, performance optimisation, and modern component architectures.
• Solid database skills including relational (PostgreSQL, SQL Server) and NoSQL (Cosmos DB, Redis) with experience in query optimisation and data modelling.
• Comfortable working with AI-assisted development tools (e.g. Claude Code, GitHub Copilot) to accelerate delivery of production-grade code.
• Experience with CI/CD tooling (GitHub Actions or Azure DevOps), containerisation (Docker), and Infrastructure as Code concepts (Terraform preferred).
• Working familiarity with Azure cloud services — particularly Azure App Service, Azure Functions, and Azure Container Apps — sufficient to design and deploy solutions within our existing Azure estate.

Desirable Technical Skills

• Genuine interest in AI/LLM technologies with some hands-on experience integrating APIs (e.g., OpenAI, Azure OpenAI) into applications.
• Familiarity with RAG patterns, vector search, and document processing pipelines for AI-enhanced applications.
• Experience with data engineering tooling such as Microsoft Fabric for building analytics and reporting pipelines.
• Experience implementing secure authentication and authorisation patterns (OAuth 2.0, managed identities) in cloud-native applications.
• Familiarity with container orchestration beyond basic Docker (e.g. Kubernetes, AKS).

Personal Qualities

• Strong architectural thinking with the ability to balance pragmatic delivery against long-term technical vision; comfortable making and communicating trade-off decisions.
• Genuine passion for mentoring and knowledge sharing; someone who raises the technical bar for the entire team rather than working in isolation.
• Intellectually curious and self-directed; stays current with the rapidly evolving technology landscape including AI/LLM developments, and proactively brings new ideas and approaches to the team.
• Effective communicator who can translate complex technical concepts for non-technical stakeholders and contribute to client-facing discussions with clarity and confidence.

Preferred Background

• Previous experience in an MSP, consultancy, or multi-client environment where you delivered solutions across varied industries and technical landscapes.

Benefits

• Private healthcare and dental cover.
• Perkbox benefits platform and Garmin smartwatch.
• Funded training and certification.
• Modern Warrington HQ with breakout spaces, games console, pool table, premium coffee and an office dog.